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Chapter 7: Computer Networks. Learning Objectives. Define a network and its purpose. Describe several uses for communications technology. Understand the various topologies and architectures a computer network might use.

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Chapter 7:

Computer Networks

learning objectives
Learning Objectives

Define a network and its purpose.

Describe several uses for communications technology.

Understand the various topologies and architectures a computer network might use.

Explain the difference between a LAN, a WAN, and a PAN, and between an intranet, an extranet, and a VPN.

learning objectives3
Learning Objectives

Understand characteristics about data and how it travels over a network.

Name specific types of wired and wireless transmission media and explain how they transmit data.

Identify different protocols that can be used to connect the devices on a network.

List several types of networking hardware and explain the purpose of each.


This chapter covers:

Networking concepts and terminology

Common networking and communications applications

Technical issues related to networks, including the major types of networks, how data is transmitted over a network, and types of transmission media involved

Explanation of the various ways networked devices communicate with one another

Various types of hardware used in conjunction with a computer network

what is a network
What Is a Network?

Network: A connected system of objects or people

Computer network: A collection of computers and other hardware devices connected together so that users can share hardware, software, and data, as well as electronically communicate with each other

Internet: Largest computer network in the world

Types of networks

Business networks

Phone networks

Home and multimedia networks

networking and communications applications
Networking and Communications Applications

Mobile phones (wireless phones)

Cellular (cell) phones

Must be within range of cell tower to function

Satellite phones

Used where cell service isn’t available

Dual-mode phones

Allows users to make telephone calls on more than one network

Cellular / Wi-Fi dual mode phone are most popular

networking and communications applications8
Networking and Communications Applications


Sending short numeric or text messages to a person’s pager

Most often used for onsite paging applications


Two-way paging

Most often takes place today via a mobile phone

networking and communications applications9
Networking and Communications Applications

Global positioning system (GPS): Uses satellites and a receiver to determine the exact geographic location of the receiver

Commonly found in cars today

Available as handheld units

Used by the military, hikers, travelers, and others who need to know their precise location

networking and communications applications10
Networking and Communications Applications

Monitoring systems: Monitor status or location of individuals, vehicles, assets, etc.

RFID-based systems

GPS-based monitoring systems

Electronic medical monitors and other types of home health monitoring

Digital entertainment

High-definition television/radio: HDTV is replacing analog broadcasts

Satellite radio: Delivers digital radio content to satellite receivers

Multimedia networking and digital data distribution

networking and communications applications11
Networking and Communications Applications

Videoconferencing: Use of communications technology for real-time, face-to-face meetings between individuals located in different places

Technology continues to improve and mimic real-life meeting environments

Telepresence videoconferenceing

Online conferencing (via the Internet)

Video phone calls

networking and communications applications12
Networking and Communications Applications
  • Collaborative computing (workgroup computing): Using a computer and communications technology to work together on documents and other project
    • Tools include Microsoft Office markup tools and collaboration software
  • Telecommuting: Individuals work at home and communicate with their place of business and clients via communications technologies
    • Possible because of the Internet and other communications technologies
networking and communications applications13
Networking and Communications Applications

Telemedicine: Use of communications technology to provide medical information and services

Remote monitoring and consultations

Remote diagnosis


types of networks
Types of Networks

Topology: How the devices in the network (called nodes) are arranged

Star networks: All devices connect to a central device or hub)

Bus networks: All devices connect to a central cable

Ring networks: Devices connect to one another in a ring

Mesh networks: Multiple connections between devices

Some networks use a combination of topologies

types of networks16
Types of Networks

Architecture : The way networks are designed to communicate

Client-server networks

Client: PC or other device on the network that requests and utilizes network resources

Server: Computer dedicated to processing client requests

types of networks17
Types of Networks

Peer-to-peer networks: All computers at the same level)

Internet peer-to-peer (P2P) computing: Performed via the Internet

types of networks18
Types of Networks

Local area network (LAN): Small geographical area (office, campus, etc.)

Wide area network (WAN): Large geographical area (Internet)

Metropolitan area network (MAN): Serves a metropolitan area

Municipal Wi-Fi projects

Personal area network (PAN): Connects personal devices for one individual, such as his or her portable PC, mobile phone, and portable printer

types of networks19
Types of Networks

Wireless sensor networks (WSNs): Contain sensors (devices that respond to a stimulus and generate an electrical signal that can be measured or interpreted)

Intranet: Private network set up by an organization for use by its employees

Extranet: Intranet that is at least partially accessible to authorized outsiders

Virtual private network (VPN): Secure path over the Internet that provide authorized users a secure means of accessing a private network via the Internet

data transmission characteristics
Data Transmission Characteristics

Analog vs. digital (waves vs. discrete)

Bandwidth: The amount of data that can be sent at during a given period of time

Measured in bits per second (bps)

Serial vs. parallel transmission

Serial = 1 bit

Parallel = atleast 1 byte ata time

data transmission characteristics21
Data Transmission Characteristics

Transmission timing

Synchronous transmission (at regular, specified intervals)

Asynchronous transmission (sent when ready)

Isochronous transmission (sent at the same time as other, related, data)

data transmission characteristics22
Data Transmission Characteristics

Transmission directions

Simplex transmission (one way only)

Half-duplex transmission (one way at a time)

Full-duplex transmission (both ways at the same time)

data transmission characteristics23
Data Transmission Characteristics

Type of connections

Circuit-switched: Dedicated path over a network is established and all data follows that path

Packet-switched: Messages are separated into small units called packets and travel along the network separately

Used to send data over the Internet

Broadcast: Data is sent out to all other nodes on the network

Primarily used with LANs

data transmission characteristics25
Data Transmission Characteristics

Wired connections: The PC is physically cabled to the network

Common in schools, business, and government facilities

Wireless connections: Typically use radio waves to send data through the air

Rapidly becoming more popular in homes and businesses

Wireless hotspots are commonly available in public locations

wired network transmission media
Wired Network Transmission Media

Twisted-pair cable

Pairs of wires twisted together

Used for telephone and network connections

Coaxial cable

Thick center wire

Used for computer networks, short-run telephone transmissions, cable television delivery

Fiber-optic cable

Glass or fiber strands through which light can pass

Used for high-speed communications

wireless network transmission media
Wireless Network Transmission Media

Use radio signals

Short-range (such as Bluetooth) can connect a wireless keyboard or mouse to a PC

Medium-range (such as Wi-Fi) are used for wireless LANs and to connect portable PC users to the Internet at public hotspots

Longer-range (WiMAX) can be used to provide Internet access to wide geographic areas

Radio frequencies are assigned by the FCC and are measured in hertz (Hz)

The electromagnetic spectrum is the range of common electromagnetic radiation (energy) that travels in waves

cellular radio transmissions
Cellular Radio Transmissions

Use cellular towers within cells

Calls are transferred from cell tower to cell tower as the individual moves

Different transmission frequencies are used to avoid interference and allow multiple conversations to take place via a single tower at one time

Widely used, but cell service not available everywhere

Cell phone technology is referred to in generations

Today’s phones are third-generation

4G service is beginning to become available

microwave and satellite transmissions
Microwave and Satellite Transmissions

Microwaves: High-frequency radio signals

Sent and received using microwave stations or satellites

Microwave stations are earth-based and can transmit signals to each other over distances of about 30 miles

Signals are line of sight, so stations are usually built on tall buildings, towers, mountaintops

Communication satellites: Space-based devices launched into orbit to send and receive microwave signals from earth

Traditional satellites use geosynchronous orbit

Low earth orbit (LEO) satellites were developed to combat delay

Medium earth orbit (MEO) satellites are most often used for GPS systems

Can send large quantities of data at high speed over long distances

infrared ir transmissions
Infrared (IR) Transmissions

Sends data as infrared light

Like an infrared television remote, IR requires line of sight

Because of this limitation, many formerly IR devices (wireless mice, keyboards) now use RF technology

IR is still sometimes used to beam data between handheld PCs or gaming systems, or send documents from portable PCs to printers

networking standards and communications protocols
Networking Standards andCommunications Protocols

Standards: A set of criteria or requirements considered to be the approved model for something

Networking standards: Address how networked computers communicate and connect

Communications protocol: An agreed-upon standard for transmitting data between two devices on a network

In networking, standards and protocols specify how:

Devices physically connect to a network

Data is packaged for transmission

Receiving devices acknowledge signals

Errors are handled

Also ensure products can work together


Ethernet: Most widely used communications protocol for wired LANs

Typically used a bus or star topology and twisted-pair, coaxial, or fiber-optic cables

Original(10Base-T)Ethernet networks run at 10 Mbps

Newer 100 Mbps, 1Gbps, and 10 Gbps versions are common

100 Gbps is in development

Power over Ethernet: Allows electrical power to be sent along with data on an Ethernet network

Most often used by businesses

tcp ip and wireless application protocol wap
TCP/IP and Wireless Application Protocol (WAP)

TCP/IP (Transmission Control Protocol/Internet Protocol): Used for transferring data over the Internet

Uses packet switching

TCP/IP support built into virtually all Oss

IPv4 uses 32-bit addresses

IPv6 uses 128-bit addresses and expected to eventually replace IPv4

Wireless Application Protocol (WAP):A standard for delivering Internet content to mobile devices

Microbrowser: Used to access WAP content

wi fi 802 11
Wi-Fi (802.11)

Wi-Fi (Wireless Fidelity): A family of wireless networking standards using the IEEE standard 802.11

Also called wireless Ethernet

Current standard for wireless networks in home and office

Designed for medium-range transmission

Wi-Fi hardware built into most notebook PCs and many consumer devices today

Hotspots rapidly multiplying

Speed and distance of Wi-Fi networks depends on

Standard and hardware being used

Number of solid objects between the access point and the PC or wireless device

Possible interference

wi fi 802 1142
Wi-Fi (802.11)

Various standards

Current standard is 802.11g

Emerging standard is 802.11n

wimax mobile wimax and mobile fi
WiMAX, Mobile WiMAX, and Mobile-Fi

WiMAX (Worldwide Interoperability for Microwave Access or 802.16): Fairly new wireless standard for longer range wireless networking connections

Designed to deliver broadband to homes, businesses, other fixed locations

Mobile WiMAX is the mobile version of the standard

4G mobile phones may be WiMAX-based

Mobile-Fi (802.20): Currently in development for providing high-speed mobile Internet access in cars, trains, and other moving vehicles

short range wireless networking
Short-Range Wireless Networking

Bluetooth: Very short range (less than 10 feet)

For communication between computers or mobile devices and peripheral devices

Bluetooth devices are automatically networked with each other when they are in range (piconets)

Ultra Wideband (UWB or WiMedia): Originally developed by the military for locating tanks, enemies, hidden objects

Designed for wireless multimedia networking

Range of 100 feet or less

Speed depends on distance between devices

New Bluetooth standards will use UWB to speed up transfers of large amounts of data

Wireless USB is UWB-based

short range wireless networking47
Short-Range Wireless Networking

Wireless HD (WiHD): In development, designed for networking home electronics devices

ZigBee: Emerging, designed for inexpensive, simple short-range networking like sensor networks

Intended for application that require low data transfer rates and several years of battery life

Can accommodate more than 65,000 devices on a single network

phoneline and powerline
Phoneline and Powerline

Phoneline (HomePNA): Allows computers to be networked through regular phone lines and jacks

Geared for quick and easy networking

HomePNA 3.0 is fast (320 Mbps) and designed for both computers and multimedia networking

Powerline: Allows computers to be networked over power lines and conventional outlets

Also designed for quick and easy networks

HomePlug AV is fast (200 Mbps) and designed for both computers and multimedia networking

Broadband over power lines (BPL): An emerging technology that allows Internet data to be sent over existing power-pole infrastructure

cellular standards
Cellular Standards

Second-generation wireless standards

GSM (Global System for Mobile communications)

CDMA (Code Division Multiple Access)

Third-generation standards

GPRS (General Packet Radio Service)

EDGE (Enhanced Data Rates for GSM Evolution)

UMTS (Universal Mobile Telecommunications System)

HSDPA (High Speed Downlink Packet Access)’

EV-DO (Evolution Data Optimized)

SMS (Short Message Service)

Fourth generation standards are under development

Some are WiMAX-based

networking hardware
Networking Hardware

Network adapter: Used to connect a PC to a network or the Internet

Also called network interface card (NIC) when in the form of an expansion card

Available in a variety of formats

PCI and PCIe


PC Card and ExpressCard

Adapter must match the type of network being used (Ethernet, Wi-Fi, Bluetooth, etc.)

Are often built into portable computers

networking hardware52
Networking Hardware

Modem: Device that connects a computer to the Internet or to another computer

Term used for Internet connection device, even if not connecting via a phone line

Type of modem needed depends on the type of Internet access being used

Conventional dial-up


Fixed wireless


These and other types of Internet access are discussed in Chapter 8

networking hardware for connecting devices and networks
Networking Hardware for ConnectingDevices and Networks

Hub: Central device that connects all of the devices on the network

Switch: Connects devices and identifies the device on the network for which the data is intended and sends the data only to that node

Wireless access point: Used to connect devices to a network wirelessly

Gateway: A devices that connects two different networks

Bridge: Usually connects wired LANs

Router: Connects networks and plans path (routes traffic)

Can be wired or wireless

other networking hardware
Other Networking Hardware

Repeater: Amplifies signals along a network

Range extender: Repeater for a wireless network

Antenna: Used when Wi-Fi networks need to go further than hardware normally allows

Higher-gain antennas can be used with routers

Some network adapters can use an external antenna

Multiplexer: Combines transmissions from several different devices to send them as one message

Concentrator: Combines messages and sends them via a single transmission medium in such a way that all of the messages are active


What Is a Network?

Networking and Communications Applications

Types of Networks

How Does Data Travel Over a Network?

Networking Standards and Communications Protocols

Networking Hardware